Introduction
Tympanic bulla osteotomy (TBO) is indicated for the management of middle and internal ear diseases.1 The surgical approach to the tympanic bulla (TB) is largely dictated by the initial disease with respect to the 2-fold rationale for surgical management: elimination of the primary cause and removal of the debris or diseased tissues from the TB.1 In dogs, middle ear disease (MED) is usually the consequence of unsuccessful medical management of chronic otitis externa.2–4 The most common approach is lateral and includes total ear canal ablation (TECA) and lateral bulla osteotomy (LBO). Ventral bulla osteotomy (VBO) is considered when the disease is limited to the TB.5
In cats, MED is common. Nasopharyngeal inflammatory polyps (NPIPs) and otitis media (OM) are more frequently diagnosed than in dogs and are often not accompanied by severe otitis externa.6–8 Malignant tumors are also less frequent than in dogs. Cats with MED associated with NPIPs are usually young and are presented with upper respiratory signs, whereas cats with neurologic signs due to concurrent otitis interna or tumors are older.7 The VBO, which provides an excellent exposure of the middle ear without damaging the external ear, is therefore more frequently indicated in cats than in dogs.6
Minimally invasive surgical techniques using natural orifices to approach deep structures, such as natural orifice transluminal endoscopic surgery, have been developed in veterinary medicine to decrease postoperative pain and hospitalization time.9 A transoral approach has been described in veterinary surgery for the removal of pituitary tumors in dogs and cats.10,11 After the exact definition of anatomic landmarks using advanced imaging, this approach is now considered to be a safe and effective option for the long-term remission of symptoms of pituitary-dependent hyperadrenocorticism.12
In dogs and in cats, the TB is situated not far away from the pituitary gland. Transoral VBO (TOVBO) has recently been described in a dog cadaveric study using a similar principle.13 It was hypothesized that the osteotomy of the TB via the oral cavity could provide a minimally invasive access for the treatment of OM and otitis interna when the external ear canal (EEC) was free of disease. This approach meets the treatment objectives of OM or TB benign tumors, particularly in cats.
When assessing the local anatomy of the TB in cats comparatively to dogs, there are some differences in the anatomy of the TB itself and the TB environment.14–18 The TB is a cavity of the temporal bone in its petrous part. It appears noticeably larger in volume in cats than in dogs.15–17 It is almost completely separated into 2 distinct cavities by the septum bullae: a large ventromediocaudal chamber (hypotympanum) and a smaller dorsolaterorostral chamber (epitympanum and mesotympanum) that contains the promontory in which the inner ear is located.16 Removal of the diseased tissues requires complete opening of the septum bullae, which is easily performed with a ventral access to the TB.
The local environment of the TB in cats is similar to the one described in dogs,13 but there are some major differences including the absence of retro-articular foramina, of a temporal meatus and of mastoid foramina in cats.14 The TB is surrounded by many important neurovascular structures. The external carotid, superficial temporal, occipital, and tympanic arteries are found on the lateral aspect of the TB. The internal jugular and caudal auricular, caudal articular, and retroarticular veins are the most important veins in this region. However, most of those arteries and veins are located on the dorsal, lateral, rostral, or caudal aspects of the TB, while the TOVBO surgical approach takes place on the rostromedial aspect.
Conversely, many cranial nerves pass through foramina located close to the TB. These nerves include rostrally the mandibular branch of the trigeminal nerve (through the oval foramen and the caudal alar foramen), laterally the facial nerve (through the stylomastoid foramen), and caudally the glossopharyngeal, vagal and accessory nerves (through the tympano-occipital fissure and jugular foramen) and the hypoglossal nerve (through the hypoglossal canal).14,19 The distribution of neural structures in the middle ear is similar to that in dogs, but the tympanic plexus is reported to be more exposed to iatrogenic trauma in cats.20–23
As described above, the important neurovascular structures surrounding the TB are especially found caudally, laterally, and ventrally. On the other hand, the rostromedial surface of the TB is easily palpable through the mouth, under the oropharyngeal mucosa. These considerations justify a transoral approach to the TB.
Before the beginning of the present study in 2015, we validated the surgical feasibility of TOVBO in cats by performing a cadaveric dissection study. All preliminary anatomic data allowed us to perform this approach in clinical cases. The present study retrospectively analyzed the short- and long-term postoperative clinical results of TOVBO for the treatment of MED in cats and explored the clinical hypothesis that TOVBO could be a treatment alternative to other VBOs.
Materials and Methods
Animals
Medical records of cats with a diagnosis of MED between February 2016 and February 2019 that underwent TOVBO at our academic hospital were reviewed, and data (age, body weight, breed, medical and/or surgical treatment prior to presentation, diagnostic imaging findings, surgical procedure, complications, laboratory results, medical treatment, and outcome) were collected. An institutional animal care and use committee was used, and owners signed a consent form before the procedure.
Surgical procedure
The procedure performed in cats was as described for dogs.13 The cat was positioned in dorsal recumbency with the head in extension and the maxilla restrained by tape over the hard palate and canine teeth. The mouth was opened and the soft palate retracted to give an access to the oropharynx. At this stage, when present, NPIPs were removed from the nasopharynx by usual (torsion) technique.8 The TB was then identified by oral palpation as a convex surface just medially and caudally to the pterygoid process of the basisphenoid bone on each side. The light was focused on this point, and a 1.5-cm incision of the oropharyngeal mucosa was performed. The soft tissues surrounding the TB were dissected with a periosteal elevator (Figure 1).
Photograph showing the transoral ventral bulla osteotomy approach in a cat. The cat is positioned in dorsal recumbency with the mouth opened. The tongue is pulled out of the mouth and placed dorsally between the mandible canine teeth. A Senn-Miller retractor rostrally grasps the soft palate on the side of the approached tympanic bulla (TB). On this view, the oropharyngeal mucosa has been incised and dissected over the TB (star).
Citation: Journal of the American Veterinary Medical Association 260, 8; 10.2460/javma.21.01.0054
The opening of the TB was performed with a 3-mm Kirschner wire that was protected, when necessary, by a sleeve. Drilling was performed at a 15° angle from the horizontal plane of the hard palate. Widening of the hole was continued with Kerrison rongeurs. The septum between the 2 chambers of the TB was opened with the same instrumentation. Samples were collected for bacterial culture and histopathological analysis. Curettage of the TB content was performed with smooth curettes associated with low-pressure lavage of the tympanic cavity with isotonic saline (0.9% NaCl) solution (Figure 2). In 3 cases, this step of the procedure was performed with video assistance. Curettage was stopped when all infected tissues or polyps were removed from the TB. The oropharyngeal mucosa was closed with absorbable suture (4-0 Glycomer 631; COVIDIEN). During all of the procedures, the cats’ mouth was closed for 5 minutes every 15 minutes in accordance with usual recommendations to avoid cerebral ischemia.24
Photograph showing curettage of the TB (asterisk). The entire TB mucosa has been curetted after opening both chambers. Copious lavage of the TB with saline (0.9% NaCl) solution has been performed.
Citation: Journal of the American Veterinary Medical Association 260, 8; 10.2460/javma.21.01.0054
Follow-up
Short-term clinical examination was conducted daily during hospitalization. The surgeon performed a complete physical examination on all cats before discharge from the hospital and 15 days after surgery. Any new clinical signs were considered as complications. Horner syndrome and peripheral vestibular syndrome that were present before surgery were not considered as surgical complications. Complications were classified as catastrophic (complication or associated morbidity that caused permanent unacceptable function, was directly related to death, or was a cause for euthanasia), major (complication or associated morbidity that required further treatment based on current standards of care, either medical or surgical), or minor (not requiring additional surgical or medical treatment to resolve (eg, bruising, seroma, or minor incisional problems).25 Complications were also divided into early (within 15 days after surgery) and late (after 15 days) complications. Computed tomography control was conducted on 1 cat (3 weeks after surgery) to plan the contralateral ear surgery and evaluate the result of the TOVBO
Long-term follow-up was performed 6 months postoperatively via an owner telephone interview, in which clinical status and owner satisfaction were assessed by a questionnaire. This owner questionnaire evaluated in particular whether the cat still demonstrated some of the clinical signs that led to the initial consultation and surgery, whether it presented local deformation or swelling or fistula, and whether there was still head tilt, falling, rolling (symptoms of peripheral vestibular syndrome), Horner syndrome (miosis, ptosis, and enophthalmos), facial paralysis (loss of pinna mobility and loss of eyelids mobility), hypoglossal nerve paralysis (asymmetry of the tongue), some deafness, blindness, dysphagia (incapacity to swallow), or some coughing or pain spontaneously or when touching the operated zone. Owners were asked whether clinical signs had recurred as well as whether additional treatment had been prescribed by the local veterinarian. They were finally asked to grade the final result on a 5% scale (complete satisfaction = 100%).
Results
Signalment, clinical signs and preoperative findings
Thirteen cats (16 TOVBOs: 10 unilateral and 3 bilateral) were included in the study. Mean age at presentation was 46 months (range, 6 months to 12 years). All cats were presented with a MED (nasopharyngeal polyp; n = 5, otitis interna; 8, or presence of a bullet in the TB; 1), with a mean time of clinical signs prior to surgery of 8.4 months (range, 2 days to 2 years). All cats but 1 had received medical treatment by their referring veterinarian before admission (local treatment, systemic antimicrobials, or anti-inflammatory drugs). Prior to surgery, 3 cats had severe (n = 2) or mild (1) peripheral vestibular syndrome and 2 cats had Horner syndrome (Supplementary Table S1). Otoscopic examination, CT, and MRI were performed in 13, 11, and 2 cats, respectively.
Surgery and postoperative period
Closure of the mucosa was performed in all 13 cats with a 4-0 absorbable suture in a cruciate mattress pattern (n = 9) or a simple continuous pattern (4). Mean time for surgery for one TOVBO (from incision to closure) was 17 minutes. No intraoperative complication was observed. In the postoperative period, all cats received artificial tears in both eyes (every 4 hours), local steroid medication (fluticasone, 1 puff every 4 hours), and oral steroid medication (dexamethasone, 0.1 mg/kg, IV, daily). Pain control was obtained by methadone administration (0.1 to 0.2 mg/kg, IV, q 4 h, depending on the pain score) and fentanyl constant rate infusion (2 µg/kg/h, IV) that was stopped at 15 hours postoperatively.
Postoperative period and complications
Mean time to discharge after surgery was 3 days (range, 1 to 7 days). One cat with a poor preoperative status that underwent a bilateral TOVBO and a ventral rhinotomy died at postoperative day 3 from pneumonia. The other cats recovered well from surgery with no upper respiratory signs, with the exception of 1 cat (case 4) that presented a slight snoring during 1 day.
Eight of 12 cats presented postoperative complications. A slight ptyalism was noted in 5 cats during the anesthesia recovery period but was considered normal after an oral procedure. During the first week after surgery, temporary blindness was observed in 1 cat during 24 hours, as well as head tilt (n = 1), Horner syndrome (3), loss of balance (2), or loss of appetite (2). At the 2-week evaluation, clinical examination was found to be normal in 9 cats. One cat presented with persistent Horner syndrome, 1 cat a residual head tilt, and 1 cat a limited otitis externa managed with a local treatment. One cat underwent 3 weeks of postoperative control CT examination, which showed that the ventral wall of the operated TB was absent and the TB was partially filled with air (Figure 3). An EEC obstruction was identified on the contralateral side, and the cat underwent a TECA.
Control CT image obtained 3 weeks after transoral ventral bulla osteotomy in a cat. The ventral aspect of the operated TB (on right side of the figure) is opened, and the TB is partially filled with air.
Citation: Journal of the American Veterinary Medical Association 260, 8; 10.2460/javma.21.01.0054
Histopathology confirmed the presence of inflammatory polyps in the tympanic cavity in 5 of 12 samples and lymphoplasmacytic OM or chronic inflammatory tissue in 3 of 12 and in 5 of 12 samples, respectively. The cat in which a TECA was performed had a histologically confirmed polyp of the EEC. Microorganisms were isolated from 8 of 12 cats and included Staphylococcus spp (n = 3), Escherichia coli (3), and Pasteurella multocida (3). Antimicrobials (amoxicillin–clavulanic acid, 20 mg/kg, PO, q 12 h) were administered in 10 of 12 cats (during 2 to 3 weeks after surgery), as well as corticosteroids (dexamethasone, 0.1 mg/kg) in all cats for 2 to 5 days after surgery. In 1 cat in which bilateral otitis externa was diagnosed during the first month after surgery, clinical signs resolved after local daily cleaning and local antimicrobial administration.
Mean time to latest follow-up was 8.6 months (range, 6.5 to 26 months). Two cats died during this period (at 12 and 19 months after surgery) for reasons unrelated to the MED (high-rise syndrome and road traffic accident, respectively). Six months after surgery, 9 of 12 cats were free of MED signs. One cat that had Horner syndrome postoperatively showed a slight residual anisocoria, and 2 out of 12 cats still presented a peripheral vestibular syndrome, which was less severe compared to the preoperative status. The 2 cats that died were free of clinical signs at the time of death. The owners did not report long-term complications or changes in the way the cat was able to breathe or eat, and their overall satisfaction was 95% (Supplementary Table S2).
Discussion
The present retrospective study confirmed the feasibility of TOVBO in cats and provided the first postoperative evaluation of this technique to address MED in cats. In this study, TOVBO was associated with postoperative complications in 8 of 12 cats and permitted resolution of MED in 9 of 12 cats. Different accesses to the TB cavity have been described. Myringotomy,26 which consists of making a small incision in the tympanic membrane, is a diagnostic and sometimes therapeutic procedure that allows collecting bacterial and cytological samples and flushing and removal of fluid accumulation from the tympanic cavity. However, it offers a limited access to the TB when firm material, such as pus, debris, granuloma, or tissues, has to be removed. McBride27 has described a more aggressive access of the TB that consists of placement of a drain through the EEC and TB into the nasopharynx. This technique can be useful to treat fluid accumulation in the TB but has not been precisely clinically documented, even if cited by previous reports26 as one of the possible treatments for OM. MacNutt and McCoy5 were the first to describe a ventral access to the TB. This surgical technique allows a complete access to the TB and facilitates its curettage and ventral drainage. Lateral bulla osteotomy has also been described.28 Lateral TBO requires TECA.29 The opening of the TB is limited to its lateroventral aspect, but curettage and drainage are possible. The last 2 techniques (VBO and TECA-LBO) are currently considered the gold standards for TB trepanation. In our study, TOVBO appeared as a simple procedure, which was less aggressive to surrounding structures than the other techniques described. Indeed, it only required a 1-cm mucosal incision and soft tissue dissection to approach the TB. The duration of the procedure also appeared shorter (17 minutes) than the other 2 techniques, which both require clipping and aseptic preparation of the patient contrary to TOVBO.
Transoral VBO can be indicated to address multiple diseases. The oral access allows the drainage of empyema and removal of granulomas and foreign bodies from the bulla in a similar manner as with VBO. Tumor removal is a particular issue. Total ear canal ablation and LBO are more effective to completely remove ear tumors in accordance with oncological surgery rules and offers a better prognosis than local excision for ceruminous carcinomas in dogs.30 We think that TOVBO should not be performed for the treatment of neoplasia, considering its inability to obtain wide margins and the high risk of spreading tumor cells with this approach. This is not the case for benign tumor-like NPIPs.8,31 These nonneoplastic masses develop from the mucosa of the nasopharynx, auditory tube, or middle ear. There are 3 main treatment options for polyp removal: traction avulsion, LBO, or VBO. The technique of choice is influenced by the polyp localization. Simple traction through the mouth is generally recognized as sufficient, with almost 30% of recurrence when no middle ear involvement is present.32 It is typically recommended to perform TBO with or without ear canal ablation when a tympanic cavity involvement is observed. A low rate of recurrence after VBO (8%) has been reported.33 Transoral VBO could be an alternative to this usual treatment scheme, allowing the removal of NPIPs with the same approach. Cholesteatomas, even rare in cats, represent an intermediate situation of this benign tumor, which necessitates complete removal of the ventral aspect of the TB as well as complete curettage of the TB. Transoral VBO could also be indicated to address this pathology.34,35
Various complications related to TB osteotomies have been reported, and the literature differentiates well those associated with VBO5,36,37 and with TECA-LBO.4,38 These include common complications reported for any surgery (eg, infection), but also more specific iatrogenic lesions due to the local anatomy of the middle ear and local environment of the TB. Some of these complications are quantified in retrospective studies while others have only been reported in clinical cases.38,39 Complications associated with TECA-LBO are numerous: significant hemorrhage, deliberate (for tumor removal) or accidental damage to the facial nerve, incisional infection, neurologic problems (Horner syndrome, vestibular syndrome, hypoglossal nerve injury), pinna necrosis, dyspnea and airways obstruction, pain, and aspiration pneumonia.39 Ventral TBO complications include Horner syndrome, vestibular disturbances and ossicle damage, wound drainage, damage of associated vascular tissues, and hypoglossal and facial nerve deficits.7,33,36 Ventral bulla osteotomy less likely affects hearing than TECA-LBO.40 This could be explained by the approach used for TECA-LBO, which necessitates removal of the tympanic membrane and at least a portion of the epitympanic recess. However, cats affected by deafness prior to surgery do not regain auditory function. The ventral approach also allows a better identification of major nervous and vascular structures present in the TB environment than with the lateral approach. In the TOVBO approach, none of the neurovascular structures encountered during the TECA-LBO and the VBO techniques are met since only the oropharyngeal mucosa is incised to reach the TB. This could explain the small number of complications observed in our small case series. In particular, there was no need for retraction of the hypoglossal or facial nerves during TOVBO so the risk of stretching and damaging these nerves was limited. The linguofacial, maxillary and the retroglenoid veins, and the lingual arteries are also potentially damaged during the TECA-LBO or VBO approaches. These complications were not encountered during the TOVBO approach, as these vessels are located far from the area of the TB being dissected. Nevertheless, we think that a particular attention should be paid during dissection of the mucosa when performing a TOVBO to limit the risks of hemorrhage. The dissection must be carried out by periosteal elevation all around the TB. In that way, the vessels are easily separated from the bulla without major bleeding. The surgeon must also preserve the lacerum and retroglenoidal foramen rostrally, from which the emissary vein and 1 maxillary artery terminal exit, respectively. In the caudomedial aspect of the TB, the dissection must be kept away from the tympano-occipital fissure that contains the cranial nerves IX, X, and XI and the roots of the internal jugular and vertebral veins.
In the light of our first clinical experience, we consider that some of the complications associated with TECA-LBO or VBO would not be encountered with TOVBO. Other complications (Horner syndrome, peripheral vestibular syndrome) are the result of TB curettage, and therefore observed in any TBO. Horner syndrome is often present after traction of an inflammatory polyp, either via the oropharynx or via the EEC. Two and 3 cats of our study demonstrated preoperative and postoperative Horner syndrome, respectively. In total, 5 of 12 cats in the present study demonstrated Horner syndrome immediately after surgery, but none still had complete Horner syndrome at the 6-month evaluation. This observation compared favorably with the results of previous studies,32–34 and Horner syndrome was associated to NPIP in all 5 cases.32,33 A peripheral vestibular syndrome was present before surgery in 3 cats and observed in 1 cat as a complication of surgery. The preoperative CT of this cat showed an enlarged volume of the TB and enlargement of the tympano-occipital fissure. Among these cats, 2 cats showed episodes of loss of balance in the long term but at a lesser degree compared to the preoperative period.
Two complications seemed to us more specific to TOVBO. Hyporexia was observed in 2 cats, during the first week after surgery. We believe that this could be related to the vestibular signs (in 1 cat) but also to the discomfort of the oral approach. Nevertheless, this clinical sign resolved progressively without any specific treatment except anti-inflammatory drug administration. Postoperative blindness was the second original observed complication. It appeared in 1 cat immediately after recovery from anesthesia and lasted for 48 hours after surgery. This complication has been reported in anesthetized cats with prolonged opening of the mouth and has been explained in a recent publication.41 Opening of the jaw increases tension on the temporalis and masseter muscles. The maxillary artery is the main source of arterial supply to the brain in cats, as there is no internal carotid artery. The rete mirabile in cats is an anastomotic branch of the maxillary artery. It is composed of extra- and intracranial parts and supplies the brain. The extracranial part of the rete mirabile and its multiple branches extend at the level of the foramen rotundum, which is situated approximately 6 mm from the temporomandibular joint. The temporomandibular joint and the muscles around it are stretched during opening of the mouth, which compromises vascular supply. In the cat, we believe that failure to respect the time frames for opening and closing of the mouth compromised normal vascular flow at the rete mirabile, therefore compromising blood supply to the brain. Blindness can be temporary, disappearing between 1 day and 6 weeks, with most cats regaining vision at an interval of 4.5 days.41
Among the reported complications of VBO, a high incidence of respiratory complications was pointed out by some surgeons, in particular when single-stage bilateral VBO was performed. This was confirmed by a large study37 that included 282 cases that recommended performing staged VBO. In our case series, 1 cat that underwent unilateral TOVBO demonstrated upper respiratory signs that disappeared after 24 hours, while there were no upper respiratory signs in the 3 cats undergoing bilateral TOVBO. Given the small sample size, no conclusion could be drawn at this stage.
Similar to VBO, TOVBO does not change ear carriage. The cats of our study did not wear an Elizabethan collar because they did not have soft tissue damage with the exception of the oropharyngeal incision that healed without complication. No coughing, regurgitation, or dysphagia was observed during either hospitalization or the long-term follow up. All the cats seemed comfortable after TOVBO.
Acute wound infection could be the result of local contamination, while chronic infection generally results from local remnant of infected deep tissues. The 6-month evaluation in the present study did not allow us to conclude about this point, but we did not observe a postoperative infection in the 12 cats.
In the only postoperative CT scan performed on 1 cat, the opening of the TB was still present but we do not know what is the exact healing process of the TB via this approach. The assessment of the healing process was carried out for VBO42 and for TECA-LBO43 in 2 experimental studies. Radiographic, macroscopic, and histomorphometric evaluations at 8 and 16 weeks showed that the lateral opening of the TB did not alter its conformation. TB regeneration did not occur at 16 weeks postoperatively. The same team studied TB healing after VBO. It was found that surgery did alter the TB cavity and that connective tissues were found over the bony defect without regeneration of the TB wall at 16 weeks postoperatively.
Limitations of the present study included the small number of patients retrospectively analyzed, the lack of systematic CT control examination to check the healing process, and the lack of longer follow-up. A longer follow-up and a CT control examination could have helped us identify the timing of complete healing and content of the TB once it was healed.
Long-term clinical evaluation could have allowed us to conclude about the persistence of neurologic symptoms in the 2 cats of our study. It is believed that, like for other techniques of TBO, neurologic signs may be permanent if they persist for more than 3 weeks.38
In conclusion, the transoral ventral approach provided a good access for bulla osteotomy in all cats of the present study and was associated with similar complications as VBO. In cats, TOVBO seems to be an acceptable, safe, and minimally invasive alternative to other approaches to the TB for addressing MED.
Supplementary Materials
Supplementary materials are posted online at the journal website: avmajournals.avma.org
Acknowledgments
The authors declare that there were no conflicts of interest.
All authors approved the version before submission and agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.
References
- 1. ↑
White RAS. Middle and inner ear. In: Johnston SA, Tobias KM, eds. Veterinary Surgery Small Animal. 2nd ed. Elsevier; 2018:2078–2089.
- 2. ↑
Gotthelf LN. Diagnosis and treatment of otitis media in dogs and cats. Vet Clin North Am Small Anim Pract. 2004;34(2):469–487.
- 3.
Matthiesen DT, Scavelli T. Total ear canal ablation and lateral bulla osteotomy in 38 dogs. J Am Anim Hosp Assoc. 1990;26(3):257–267.
- 4. ↑
White RAS, Pomeroy CJ. Total ear canal ablation and lateral bullotomy in dog. J Small Anim Pract. 1990;31(11):547–553.
- 6. ↑
Trevor PB, Martin RA. Tympanic bulla osteotomy for treatment of middle-ear disease in cats: 19 cases (1984–1991). J Am Vet Med Assoc. 1993;202(1):123–128.
- 7. ↑
Fan TM, de Lorimier LP. Inflammatory polyps and aural neoplasia. Vet Clin North Am Small Anim Pract. 2004;34(2):489–509.
- 8. ↑
Anderson DM, Robinson RK, White RAS. Management of inflammatory polyps in 37 cats. Vet Rec. 2000;147(24):684–687.
- 9. ↑
Brun MV, Silva MA, Mariano MB, et al. Ovariohysterectomy in a dog by a hybrid NOTES technique. Can Vet J. 2011;52(6):637–640.
- 10. ↑
Meij BP, Voorhout G, Van den Ingh TS, Hazewinkel HA, Van’t Verlaat JW. Transsphenoidal hypophysectomy in Beagle dogs: evaluation of a microsurgical technique. Vet Surg. 1997;26(4):295–309.
- 11. ↑
Meij BP, Voorhout G, van den Ingh TS, Rijnberk A. Transsphenoidal hypophysectomy for treatment of pituitary-dependent hyperadrenocorticism in 7 cats. Vet Surg. 2001;30(1):72–86.
- 12. ↑
Meij BP, Voorhout G, Rijnberk A. Progress in transsphenoidal hypophysectomy for treatment of pituitary-dependent hyperadrenocorticism in dogs and cats. Mol Cell Endocrinol. 2002;197(1-2):89–96.
- 13. ↑
Manou M, Moissonnier PHM, Jardel N, Tissier A, Vallefuoco R. Transoral approach for ventral tympanic bulla osteotomy in the dog: a descriptive cadaveric study. Vet Surg. 2017;46(6):773–779.
- 14. ↑
Barone R. Ostéologie, tête osseuse du chat. In: Barone R, ed. Vol 1. Anatomie Comparée des Mammifères Domestiques. Vigot Frères; 2010:285–287.
- 15. ↑
Hudson LC, Hamilton WP. Cardiovascular system. In: Hudson LC, Hamilton WP, eds. Atlas of Feline Anatomy for Veterinarians. WB Saunders Co; 1993:92–93.
- 16. ↑
Hudson LC, Hamilton WP. Nervous system. In: Hudson LC, Hamilton WP, eds. Atlas of Feline Anatomy for Veterinarians. Saunders; 1993:206–207.
- 17. ↑
Boyd JS. Head and neck. In: Boyd JS, Paterson C, May AH, eds. Color Atlas of Clinical Anatomy of the Dog and Cat. 2nd ed. Mosby; 2000:15–63.
- 19. ↑
Gomes E, Degueurce C, Ruel Y, Dennis R, Begon D. Anatomic study of cranial nerve emergence and associated skull foramina in cats using CT and MRI. Vet Radiol Ultrasound. 2009;50(4):398–403.
- 20. ↑
De Lahunta A, Glass E. Veterinary Neuroanatomy and Clinical Neurology. 3rd ed. Saunders Elsevier; 2009:173–184.
- 21.
Matthews B, Robinson PP. The course of post-ganglionic sympathetic fibers distributed with the trigeminal nerve in cat. J Physiol. 1980;303:391–401.
- 22.
Matthews B, Robinson PP. The course of postganglionic sympathetic fibers distributed with the facial nerve in the cat. Brain Res. 1986;10:382(1):55–60.
- 23. ↑
Zwueste DM, Grahn BH. A review of Horner’s syndrome in small animals. Can Vet J. 2019;60(1):81–88.
- 24. ↑
Martin-Flores M, Scrivani PV, Loew E, Gleed CA, Ludders JW. Maximal and submaximal mouth opening with mouth gags in cats: implications for maxillary artery blood flow. Vet J. 2014;200(1):60–64.
- 25. ↑
Cook JL, Evans R, Conzemius MG, et al. Proposed definitions and criteria for reporting time frame, outcome, and complications for clinical orthopedic studies in veterinary medicine. Vet Surg. 2010;39(8):905–908.
- 27. ↑
McBride NL. Drainage of the tympanic bulla. In: Proceedings of the 19th Annual Convention of the AVMA. AVMA; 1953:247.
- 28. ↑
Mason LK, Harvey CE, Orsher RJ. Total ear canal ablation combined with lateral bulla osteotomy for end-stage otitis in dogs-results in 30 dogs. Vet Surg. 1988;17(5):263–268.
- 29. ↑
Bacon NJ, Gilbert RL, Bostock DE, White RA, et al. Total ear canal ablation in the cat: indications, morbidity and long-term survival. J Small Anim Pract. 2003;44(10):430–434.
- 30. ↑
Marino DJ, MacDonald JM, Matthiesen DT, et al. Results of surgery and long term follow up in dogs with ceruminous gland adenocarcinoma. J Am Anim Hosp Assoc. 1993;29(6):560–563.
- 31. ↑
Swales N, Foster A, Barnard N. Retrospective study of the presentation, diagnosis and management of 16 cats with otitis media not due to nasopharyngeal polyp. Feline Med Surg. 2018;20(12):1082–1086.
- 32. ↑
Kapatkin AS, Matthiesen DT, Noone KE, et al. Results of surgery and long-term follow-up in 31 cats with nasopharyngeal polyps. J Am Anim Hosp Assoc. 1990;26(4):387–392.
- 33. ↑
Faulkner JE, Budsgerg SC. Results of ventral bulla osteotomy for treatment of middle ear polyps in cats. J Am Anim Hosp Assoc. 1990;26(5):496–499.
- 34. ↑
Greci V, Travetti O, Di Giancamillo M, et al. Middle ear cholesteatoma in 11 dogs. Can Vet J. 2011;52(6):631–636.
- 35. ↑
Travetti O, Giudice C, Greci V, Lombardo R, Mortellaro CM, Di Giancamillo M. Computed tomography features of middle ear cholesteatoma in dogs. Vet Radiol Ultrasound. 2010;51(4):374–379.
- 36. ↑
Sharp NJH. Chronic otitis externa and otitis media treated by total ear canal ablation and ventral bulla osteotomy in thirteen dogs. Vet Surg. 1990;19(2):162–166.
- 37. ↑
Wainberg SH, Selmic LE, Haagsman AN, et al. Comparison of complication and outcome following unilateral, staged bilateral, and single-stage bilateral ventral bulla osteotomy in cats. J Am Vet Med Assoc. 2019;255(7):828–836.
- 38. ↑
Smeak DD. Management of complications associated with total ear canal ablation and lateral bulla osteotomy in dogs and cats. Vet Clin North Am Small Anim Pract. 2011;41(5):981–994.
- 39. ↑
Spivack RE, Elkins DA, Moore GE, Lantz GC. Postoperative complications following TECA-LBO in dogs and cats. J Am Anim Hosp Assoc. 2013;49(3):160–168.
- 40. ↑
Anders BB, Hoelzler MG, Scavelli TD, Fulcher RP, Bastian RP. Analysis of auditory and neurologic effects associated with ventral bulla osteotomy for removal of auditory polyps and nasopharyngeal masses in cats. J Am Vet Med Assoc. 2008;233(4):580–585.
- 41. ↑
Stiles J, Weil AB, Packer RA, Lantz GC. Post-anesthetic cortical blindness in cats: twenty cases. Vet J. 2012;193(2):367–373.
- 42. ↑
da Silva AM, de Souza WM, de Carvalho RG, Machado GF, Perri SH. Morphological aspects of tympanic bulla after ventral osteotomy in cats. Acta Cir Bras. 2008;24(3):177–182.
- 43. ↑
Da Silva AM, de Souza WM, de Carvalho RG, Machado GF, Perri SH. Morphological aspects of tympanic bulla after lateral osteotomy in cats. Acta Cir Bras. 2008;23(2):198–203.
